Radio communication system

ABSTRACT

A novel radio communication system is disclosed, the system having particular applicability and utility as a radio navigation aid. A transmitting means is utilized which, in the preferred inventive embodiment, comprises a plurality or array of antennas disposed in fixed spaced-apart relationship with one another at a known location. One of the transmitting antennas transmits a reference signal, preferably a carrier wave, modulated by a first frequency or frequencies. The remaining transmitting antennas each transmits a single or double sideband suppressed carrier signal produced by respectively different modulating frequencies for each signal. These different modulating frequencies bear a harmonic or multiple relationship with the first modulating frequency or frequencies. In the preferred inventive embodiment, each of the remaining transmitting antennas are disposed at different distances from the first or reference transmitting antenna. The novel system further includes receiver and signal processing means disposed either at the same or different locations remote from the location of the transmitting means. The receiver means generates from the received reference signal a signal having the frequency and phase of the first modulating signal at the transmitter. From this signal, the other modulating signals coherent with the first signal are derived. The receiver/signal processing means derives from the other received signals the second, third, and fourth modulating signals, and compares the phases of the signals of like frequency. In an alternative embodiment wherein the receiver means and signal processing means are disposed at different remote locations, and each receives the signals transmitted by the transmitting array, the receiver means serves only to detect the various modulating frequencies, and then retransmits the detected frequencies to the signal processing means for phase comparison. In each instance, the detected phase differences are indicative of the relative angular direction of the receiver means from the transmitting array. In the preferred embodiment, the antennas of the transmitting array are disposed on a line and the phase difference detected represents the angular deviation of the receiver from a plane bisecting and perpendicular to the line of transmitting antennas. The accuracy of the system is determined by the maximum spacing between a pair of antennas in the array. The other antennas are used only for resolving ambiguities.

Tlnited States Patent Fleming et a1.

RADIO COMMUNICATION SYSTEM Inventors: James Evans Fleming, Fairfax;

Clarence A. Lovell, McLean; James M. Bandle, Alexandria, all of Va.

[73] Assignee: Air Land Systems Co., Fairfax, Va.

[ Notice: The portion of the term of this patent subsequent to May 23,1989, has been disclaimed.

[22] Filed: Nov. 18, 1970 211 App]. No.: 90,598

Related US. Application Data [63] Continuation-in-part of Ser. No.14,031, Feb. 25,

[52] US. Cl. 343/102 [51] Int. Cl. G01s l/08 [58] Field of Search343/102, 105

[56] References Cited UNITED STATES PATENTS 3,082,419 3/1963 Crossland343/105 LS 3,117,319 l/l964 Stover 343/102 X 3,400,399 9/1968 Kline343/102 X Primary Examiner-Benjamin A. Borchelt AssistantExaminerRichard E. Berger Att0rneyDennis O. Kraft and Herbert I. Cantor[57] ABSTRACT A novel radio communication system is disclosed, thesystem having particular applicability and utility as a radio navigationaid. A transmitting means is utilized which, in the preferred inventiveembodiment, comprises a plurality or array of antennas disposed in fixedspaced-apart relationship with one another at a known location. One ofthe transmitting antennas transmits a reference signal, preferably acarrier wave, modulated by a first frequency or frequencies. Theremaining transmitting antennas each transmits a single or dou- RECEIVERY A67 I69 RECEIVER ]*Nov. 20, 1973 ble sideband suppressed carriersignal produced by respectively different modulating frequencies foreach signal. These different modulating frequencies bear a harmonic ormultiple relationship with the first modulating frequency orfrequencies. In the preferred inventive embodiment, each of theremaining transmitting antennas are disposed at different distances fromthe first or reference transmitting antenna.

In an alternative embodiment wherein the receiver means and signalprocessing means are disposed at different remote locations, and eachreceives the signals transmitted by the transmitting array, the receivermeans serves only to detect the various modulating frequencies, and thenretransmits the detected frequencies to the signal processing means forphase comparison.

In each instance, the detected phase differences are indicative of therelative angular direction of the receiver means from the transmittingarray. In the preferred embodiment, the antennas of the transmittingarray are disposed on a line and the phase difference detectedrepresents the angular deviation of the receiver from a plane bisectingand perpendicular to the line of transmitting antennas. The accuracy ofthe system is determined by the maximum spacing between a pair ofantennas in the array. The other antennas are used only for resolvingambiguities.

24 Claims, 13 Drawing Figures y TRANSMITTER ANTENNA ARRAY TRANSMITTERCOMPARATOR p m gnuuvzoma 3374209 SHEET 1 0f 6 TAROET I DIRECTION I A I dA (20 I2 I4 I l6 18 IO q FIG./ I E E B" l I I I v T r I r IMOOULATORMODULATORI- MODULATOR MODULATOR 253] I I I I l 1 K1 4 POWER SWITCHING 46I OIvIOER IADDER MEANS F1612 O I I m 40 [Q \44 I 7 PROGRAM- REOSCILLATOR FREQUENCY CONTROL SCILLATOR (IOOO Hz) MULTIPLIER MEANS 2g) 33 9 FIG. 3

-II f6 Ic+II fc+f2 Ic+f3 fc+f I I I I I I I I I f +f4 2 4 C- c-fz HI nc+ c+f2 c 3 INVENTORS JAMES E. FLEMING CLARENCE ALOVELL By JAME M.BANOLE fiw D do, 47/47 4 511 74.

ATTORNEYS PAIEIIIEIIIIIvzmm 3.774209 SHLEI 5 OF 6 Ies I6! RECEIVER- y KTRANSMITTER Y Y Y/ ANTENNA ARRAY TRANSMITTER I67 I69 I/ RECEIVERCOMPARATOR F16 8 I 37 [m /l75 I79 A M DIPLEXER MIXER DETECTOR I |77LOCAL OSCILLATOR TRANsMITTER MODULATOR FIG. .9

INVENTOR JAMES E. FLEMING CLARENCE A. LOVELL JAMES M. BANDLE ATTORN E Y5PATENTED "072N973 3,774,209

SHEET 8 OF 6 F l 6. I0

fC TC +fI fc fz RECEIvER 190 6 A IO )i/ IS I TRANSMITTER L PHASEDANTENNA ARRAY j 2I2 TRANSCEIVER F I G. I]

RECEIVER RECEIVER COMPARATOR 2I4 2|2 f FILITER FREQ DETECTUR DIFFERENCEf2 ,zle

DETECTOR FILTER 218 228 224 FIG. 13

f PHASE FREQ. FILTER DETECTOR MULTIPLY T OUTPUT f4 PHASE REQ. FILTERDETECTOR MULTIPLY 220 OUTPUT 230 -22s INVENTORS F[6 12 JAMES E. FLEMINCCLARENCE A.LOvELL I I I I I JAMES M. BANDLE o c e :2 E a a a a ATTORNEYSRADIO COMMUNICATION SYSTEM This application is a continuation-in-part ofcopending application Ser. No. 14,031 filed February 25, 1970 now US.Pat. No. 3,665,468.

The invention disclosed herein generally relates to radio communicationsystems and particularly concerns a radio communication system which hasspecific utility as a position location device or a navigational aid.

The primary requirement of a position locating or navigational system isto fix or determine the position of an object in a known frame ofreference. The accuracy of the determination varies with environmentalfactors but, as a practical matter, the greater the accuracy, the morethe value of the system. An important object and feature of the instantinvention concerns the accuracy achieved in this respect. Furtherrequirements of a position locating or navigational system comprisingobjects met by the instant invention relate to low cost and reliabilitywhich result from use of minimum amounts of electronic equipments toaccomplish its purpose.

The instant invention specifically provides a capability whereby theangular direction of a remotely disposed receiver can be derived withrespect to a line joining two antennas in a single transmitting arrayeither independently by the receiver or in conjunction with a signalprocessor disposed at a remote location, all from the transmittedsignals. A position fix in a two dimensional space requires twotransmitting arrays, and in three dimensional space three such arraysare required for a position determination. Thus, the present inventionis an important element in a position location or navigation systemrather than being such a system itself.

One component of the novel system for accomplishing these and otherobjects comprises means for generating a plurality of distinctivesignals and transmitting each signal from a separate antenna in anarray. A reference signal is produced by modulating a carrier with afirst modulating signal to produce a carrier and one or two side-bandswhich are transmitted from a first or reference antenna. A plurality ofother information signals are produced by modulating the same carrierwith other modulating signals which comprise different harmonics of andare coherent with the first modulating signal. A number of antennasspaced apart in an array are used, one to transmit each of thedistinctive signals so produced.

In one preferred embodiment of the invention, the carrier and onesideband is suppressed from each modulator output and a single frequencyis transmitted. In another preferred embodiment the carrier issuppressed from each modulator output and the two sideband frequenciesare transmitted.

At a remote location another component of the system is disposed andpreferably comprises a receiver/- signal processor means or unit whichreceives the composite signal from the transmitter array, derives fromthe reference signal a signal having the identical frequency and phaseof the first modulating signal used to produce the reference signal atthe transmitting array, multiplies this signal frequency by factors toproduce each of the other modulating signals used at the transmitter,coherent with the first derived signal, and derives from the signalcomponents transmitted from the other respective antennas of thetransmitting array the respective modulating signals used to produce thetransmitted signals. The receiver means compares the phases of signalshaving like frequencies, resolves the ambiguities of the system, and, inthe preferred embodiment, generates an output indicative of the angulardirection of the receiver from a plane that bisects the line of thetransmitting array and is perpendicular to it. In the respectiveembodiments of the inventive system, a receiver means suitable for usewith the respective transmitted signals is utilized.

In still a further alternative embodiment, the receiver means and signalprocessing means are disposed at different remote locations and eachreceives the signals transmitted by the transmitting array. The receivermeans comprises a receiver transmitter and serves only to detect thevarious modulating frequencies, and then retransmits the detectedfrequencies to the signal processing means for phase comparison.

The invention will be better understood and further advantageousfeatures and aspects thereof will become apparent from the followingdetailed description of preferred inventive embodiments, whichdescription refers to the appended sheets of drawings, wherein:

FIG. 1 schematically depicts a transmitting antenna array utilized toradiate signals having various frequency components in accordance withthe instant invention;

FIG. 2 schematically depicts, in block diagram format, a transmissionmeans coupled to the antenna array of FIG. 1, which transmission meansserves to generate the signals utilized in the instant inventive system;

FIG. 3 is a graphical representation of the various frequency componentstransmitted in accordance with one embodiment of the instant inventionutilizing suppressed carrier, single sideband transmission for allexcept the reference antenna;

FIG. 4 is a schematic representation of the frequencies transmitted byyet another embodiment of the instant invention utilizing suppressedcarrier, double sideband transmitting techniques for all except thereference antennas;

FIG. 5 is a schematic block diagram of a receiving means utilized inaccordance with the instant invention and specifically contemplated foruse with a transmission means generating frequency components asdepicted in FIG. 3;

FIG. 6 is a schematic block diagram circuit illustrative of anotherembodiment of a receiver means constructed in accordance with theinstant invention and utilized in conjunction with frequency componentstransmitted as is depicted in FIG. 3;

FIG. 7 is an electrical schematic block diagram of yet anotherembodiment of a receiver means constructed in accordance with theinstant invention and utilized to receive signals having frequencycomponents such as depicted in FIG. 4;

FIG. 8 is a diagramatic illustration of a further embodiment of theinvention wherein separate receiver means and signal processor means areutilized, and are disposed at different remote locations with respect tothe transmitting antenna array;

FIG. 9 is a schematic block diagram of a receiver means particularlysuited for use in the embodiment of the invention depicted in FIG. 8;

FIG. is a schematic representation of the frequencies transmitted by amodified embodiment of the invention depicted in FIG. 8;

FIG. 11 is a diagrammatic illustration of a modified embodiment of theinvention depicted in FIG. 8;

FIG. 12 is a schematic representation of the frequencies transmitted ina further embodiment of the instant invention; and

FIG. 13 is a simplified schematic block diagram of a receiving meansspecifically contemplated for use with a transmitting array generatingthe frequency components of FIG. 12.

Referring now specifically to the drawings, and particularly to FIG. 1thereof, a transmitting antenna array 10 is depicted contemplated forutilization in the inventive system. The transmitting antenna array willbe seen to incorporate a plurality of spaced-apart transmitting antennas12, 14, 16 and 18, respectively. In the preferred inventive embodiment,these transmitting antennas are disposed along a line 20.

As should be apparent, the antenna array 10 is similar in its structuralconfiguration to known interferometer-type antenna arrays and primarilydiffers from the known interferometer-type antenna arrays by the factthat the antennas of the instant invention are utilized to transmitsignals, rather than to receive the same. Digressing for a moment atthis juncture, some explanation of interferometer measuring techniquesis deemed useful so as to ensure a full understanding and appreciationof the instant invention, for, and as will be gleaned from thedescription hereinbelow, the novel invention makes use of manyinterferometer principles in deriving the positional information and theangular direction of a remote receiver from the antenna array 10.

Now, a conventional interferometer is a receiving apparatus and servesto indicate the angular direction to a remote signal source. From aconceptual and basic structural standpoint, a conventionalinterferometer serves to receive a single radio frequency transmittedfrom a single remote source but receives this single radio signalthrough two or more separate antennas disposed in the configuration ofan antenna array. The relative phases of the signals received by each ofthe antennas are compared with one another. Any phase differencesdetected are caused by differences in distances from the remote signalsource to each of the respective receiving antennas. Accordingly,detected phase differences between the received signals in aninterferometer can provide a direct indication of the differences indistances travelled by the respective received signals.

As is shown in FIG. I, the path length difference between a signalemanating from a remote source that hypothetically would be received byantenna 18 as compared with a signal emanating from the same remotesource hypothetically received by antenna 12 is indicated by thereference letter d. Since the spacing between antennas l2 and 18 isknown, the determination of the path length difference d along with theknown antenna spacing can directly indicate the angular direction a tothe signal source indicated by the target direction lines.

However, the mere provision of two spaced-apart atennas in aninterferometer cannot resolve differences in path lengths from theantenna to the remote signal source without some ambiguity which ariseswhenever the antennas of the interferometer are separated by distancesgreater than a half wave length of the transmitted signal. This is truesince the same phase difference between signals hypothetically receivedat antennas l8 and 12 may be indicated when the remote signal source ortarget is in different positions. Expressed from a mathematicalstandpoint, if d, the range difference, equals (n+ the phasemeasurement, qb, would be the same for values of a corresponding to 1+4), 2+.3+. etc.

In an interferometer system, these ambiguities are resolved through theutilization of more than one antenna pair (l2, 18) having a range ofspacings from one another. For example, two additional antennas such asantennas l4 and 16 could be provided in a conventional interferometerand the spacings between antennas l2 and 14 could be one half wavelength of the transmitted frequency, whereas the spacing betweenantennas 14 and 16 could be two and one half times the transmitted wavelengths, and the spacing between antennas l6 and 18 could be 12 and onehalf times the transmitted wave lengths in an antenna arrayconfiguration such as shown in FIG. 1. With this type of configuration,the accuracy of the angular measurement depends only upon the antennapair 12 and 18 whereas the other antenna pairs are utilized merely toresolve the above-mentioned ambiguities.

Interferometer techniques, however, are techniques that are related to asystem for receiving signals transmitted from a single remote sourceand, as such, interferometer techniques can be utilized since the samesignal frequency is received by all antennas of the antenna array andsince the signal received by each of the antennas is known to have beenpropagated over a particular path from a single source. Thisdiscrimination is not possible with a single frequency when aninterferometer antenna system is utilized as a transmitting antennaarray. As will be appreciated, a receiver that is located at somedistant point could not separate from the received composite signals astransmitted by a transmitting antenna array, the component signalstransmitted by each of the respective antennas of the array.

Herein, however, lies one of the basic concepts of the instant inventionas the invention contemplates the utilization of interferometer-typeprinciples in a transmitting antenna array, which invention solves theproblem of discrimination as discussed above by transmitting a differentfrequency from each antenna of the transmitting antenna array, thesefrequencies, however, bearing a coherent relationship to each other.Specifically, the novel invention contemplates the utilization ofdistinctive modulations on a single rf carrier as the signalstransmitted by each of the respective antennas of the array 10.

Having this background now firmly in mind, reference is again made toFIG. 1 of the drawings. As pointed out above, each of the antennas 12,14, 16 and 18 are each contemplated to transmit a signal generated fromthe same carrier frequency, but modulated by different and distinctivefrequencies. Further, and assuming that antenna 12 comprises a first orreference antenna, it will transmit the carrier in addition to themodulation products while for each of the antennas 14, 16 and 18 thecarriers are suppressed and only the modulation products aretransmitted. The modulation frequencies used to produce signals forantennas 14, 16

and 18 respectively are distinct multiples of the reference modulatingfrequency for the signal transmitted by antenna 12. In one alternativeembodiment, each of these multiples may bear the same relationship toone another as do the differences in spacing from each of the antennasl4, l6 and 18, respectively, to the reference antenna 12.

Expressed in a different manner, and for purposes of the ensuingdescription, let it be assumed that the reference antenna 12 transmitsan rf signal modulated by a frequency of 1,000 hz. No coherentrelationship need exist between the rf carrier signal and the 1,000 hz.modulating signal and amplitude modulation is contemplated to beutilized such that the composite signal generated by the referenceantenna 12 would comprise a carrier with one or two sidebands. Now, a2,000 hz. tone modulating a carrier may with the carrier suppressed, beutilized as the signal transmitted by antenna 14. The signal transmittedwith the carrier suppressed by antenna 16, for example, could comprisethe carrier wave modulated by a frequency of 10,000 hz. with the carriersuppressed and the signal transmitted by antenna 18, for example, couldcomprise the carrier signal modulated by a frequency of 50,000 hz. withthe carrier suppressed. It should be noted that each of the modulatingfrequencies are coherent with respect to one another.

Referring now to FIG. 2, a transmitting means is depicted, thistransmitting means being utilized to drive the antenna array of FIG. 1.The transmitter means incorporates an rf oscillator 22 coupled to apower divider 24, the output of which is utilized to drive each of fourmodulators 26, 28, 30 and 32, respectively, each of the modulators, inturn, being respectively coupled to antennas l2, l4, l6 and 18 of theantenna array 10. The signal generated by the rf oscillator 22 comprisesthe carrier wave for each of the signals transmitted and may have afrequency of 1,000 khz., for example. The modulating frequency for eachof the transmitting antennas of the array 10 is produced by anoscillator 34 which may generate a signal having a frequency of 1,000hz., for example, this signal being utilized as a reference tone.Specifically, the 1,000 cycle signal from oscillator 34 passes throughan adder means 36 into modulator 26 coupled with a first or referencetransmitter 12. Now, modulator 26 is contemplated to comprise a standardAM device in this embodiment and, thus, the signal transmitted by thefirst or reference antenna 12 of the phased antenna array 10 comprises astandard, double sideband carrier having the frequency of the rfoscillator 22 modulated by the reference tone from oscillator 34.

The output from oscillator 34 is also utilized to produce each of theother modulating frequencies or information signals subsequentlydelivered to the other antennas 14, 16 and 18 of the antenna array 10.To achieve this, the oscillator 34 output is sent to a frequencymultiplier 38 in which coherent and multiple frequencies of theoscillator frequency are produced. Specifically, the output fromfrequency multiplier 38 is placed on output lines 40, 42 and 44, whichlines respectively will have signal frequencies present of 2,000 hz.,10,000 hz., and 50,000 hz., respectively, these signals being coherentwith each other. The output from the frequency multiplier 38 passesthrough a switching means 46, the function of which will be discussed asthe description proceeds, and then to modulator means 28,

30 and 32, and specifically such that the 2,000 cycle signal ispresented to modulator 28, and 10,000 cycle signal is presented tomodulator 32. As is indicated, modulators 28, 30 and 32 are respectivelycoupled to antennas 14, 16 and 18 of the array.

As has also been discussed, the signals generated for each of the otherantennas l4, l6 and 18 are contemplated in this embodiment to comprise asingle sideband with carrier suppressed and modulator means 28, 30 and32 are accordingly constructed. In another embodiment of the invention,the signals transmitted by antennas l4, l6 and 18 may be of the doublesideband carrier suppressed variety and for this case, other suitablemodulator means 28, 30 and 32 will be provided.

In the event that the invention is utilized in its one basic embodimentwherein the first or reference transmitter 12 transmits a carrier famplitude modulated in double sideband manner by frequency f,, and thateach of the other antennas l4, l6 and. 18 transmits a suppressed carriersingle sideband signal having respective frequenciesf +f ,f +f andf +fthen the composite signal transmitted by the antenna array 10 would havethe frequency components as indicated in FIG. 3. On the other hand, ifthe embodiment of the invention is utilized wherein each of the otherantennas 14, 16 and 18 transmit suppressed carrier double sidebandsignals, then the composite output signal from the transmitting antennaarray 10 would have the components indicated in FIG. 4. It should beunderstood at this point that the particular form of transmitter meansutilized is not critical to the instant invention as all that need beprovided is a suitable transmitter means capable of producing outputs tothe respective antennas of the array having the desired frequencycomponents, such as depicted in either of FIGS. 3 or 4, and suchtransmitter means will be obvious to those of ordinary skill in the art.

When the composite signals of either FIG. 3 or FIG. 4 are transmitted toa receiver means located at some remote location yet disposed in a planeperpendicular to the line 20 of the transmitting antennas 12, 14, 16 and18, it would appear to the receiver as though only a single transmittingantenna were present, this antenna transmitting a carrier wave amplitudemodulated with the various component frequencies f f jg, and f However,as the position of the remote receiver is moved from this perpendicular,bisecting plane, the phases of the signals f, f f, f;, and f, f,,respectively, transmitted by antennas 14, 16 and 18, will shift withrespect to the phase of the reference signal transmitted by thereference antenna 12 and it is this phase shift that is utilized in theremote receiver means to determine the locus of possible receiverpositions relative to the antenna array 10, or more specifically, theangular deviation of the remote receiver position from a planeperpendicular to and bisecting line 20 of the antenna array 10. Withthis operational principle in mind, attention is now directed to theremaining figures of the drawings wherein suitable receiver means fordetermining the angular deviation of the receiver position areillustrated.

One such receiver means specifically contemplated for use with atransmitting antenna array generating signal components such as shown inFIG. 3 is illustrated in FIG. 5 and will be seen to comprise a standardAM front end including the receiving antenna 50, a first mixer 52 drivenby local oscillator 54, an intermediate frequency amplifier 56, theoutput of which is coupled to a second mixer 58 driven by a second localoscillator 60, an amplifier 62, and an AM detector 64, this receivingapparatus utilizing superheterodyne techniques. The output of thedetector 64 comprises frequency componentsf,,f ,f andf,, and, in theexample utilized, these components themselves would comprise frequenciesof 1,000, 2,000, 10,000 and 50,000 hz., respectively. Frequencycomponent f, passes through a l KHZ filter 66 and passes through avoltage controlled phase shifter 68 which selectively serves to shiftthe phase of the 1,000 KHZ signal a predetermined amount in accordancewith the voltage signal present on the control line 70 thereof. The1,000 KHZ signal then passes to various frequency multipliers 72, 74 and76 wherein the signal is respectively multiplied by two, by 10, and by50 with conventional techniques.

The detector 64 is also coupled to filters 78, 80 and 82 which serve topass only the 2 kilocycle, l kilocycle, and S0 kilocycle signals,respectively, corresponding to signalsf ,f andf.,. The output fromfilters 78, 80 and 82 comprises signals f ,f f.,, respectively, asactually received by the receiving apparatus and these outputs form oneof the inputs to phase detectors 84, 86 and 88, respectively. The otherinputs to the phase detectors 84, 86 and 88 are the signals generated byrespective frequency multipliers 72, 74 and 76, these signals having thesame respective frequencies as the frequencies of detected signalsf ,f,f,, but having a phase determined by the phase of the received signalf, passing through the l KHZ filter 66 and as shifted by the phaseshifter 68.

Now, for example, the phase of the signal synthesized from frequencymultiplier 76 corresponding to the signal having the frequency componentf is compared with the phase of the signal having frequency componentf,actually received by the receiver means passing through the 50 KHZfilter 82 in the phase detector 88. Any phase difference between thesynthesized signal and the actually received signal of the samefrequency f. produces an output from phase detector 88 which output issent through an appropriate weighing resistor arrangement 90 to anintegrating operational amplifier 92. The output from the operationalamplifier 92 appears as a voltage on line 70 operating as thecontrolling influence over a conventional phase shifter 68, the systemthus forming a servo loop which will tend to drive the phase shifter 68to an angular position of its shaft, for example, wherein null phasedifference exists. In a sequential fashion, through manual or automaticsequential actuation of switches 73, 75, and 77, for example, each ofthe other received signals having frequency components f and f arerespectively phase compared with the derived or synthesized signalhaving frequency components f and f in phase detectors 86 and 84,respectively, the outputs of which phase detectors are also sent throughthe appropriate weighting resistor arrangement 90 to the operationalamplifier 92. In each instance, the system forms a closed servo loop andproduces an output voltage in line 70 tending to drive the shaft ofphase shifter 68 to a new position, for example, to null the outputs ofphase detectors 84 and 86. The amount of phase shifting necessary inphase shifter 68, i.e., the total angular movement, for exampie, is readby any suitable output means 94, coupled to phase shifter 68, thisoutput being indicative of the relative position of the receiver meanswith respect to the transmitting antenna array and specifically beingindicative of the angular deviation of the remote receiver means from aplane bisecting and perpendicular to line 20 interconnecting each of theantennas of the phased antenna array 10.

The overall system, of course, must be calibrated so as to ensureaccuracy and, in this respect, the novel system has means to effect thetransmission of a calibration signal from the antenna array 10, thiscalibration signal being such that, to the receiver means at the remotelocation, it would appear that the receiver means is disposed on theplane perpendicular to and bisecting line 20 of the phased antenna array10, regardless of the actual position of the receiver means. In thisfashion, the receiver means can be calibrated or zeroed in". Referringagain to FIG. 2 of the drawings, the means by which this calibrationsignal is generated will be explained. The various modulatingfrequenciesf f f andf, are switched from the various antennas 12, l4, l6and 18 of the transmitting means such that each of these modulatingfrequencies appear only at the reference transmitting antenna 12. Thisswitching is accomplished by switching means 46, and is controlled asdesired by a programmed control means 94 coupled thereto. Accordingly,the output from the frequency multiplier 38 is directly switched backinto the adder means 36 through the switching means 46 such that theoutput from adder 36 comprises all the signals shown in FIG. 3, thesesignals all being utilized to amplitude modulate the carrier transmittedby antenna 12, this modulation being effected by modulator 26. Sinceantennas 14, 16 and 18 of the antenna array 10 are fed by singlesideband suppressed carrier modulators, negligible rf power will begenerated by each of the other transmitters when the modulating tones ff and f, have been removed in the calibration process.

The remote receiver means accordingly would receive the composite signaltransmitted by the single antenna 12 and this signal would be the sameas that received by the remote receiver means during normal operation ofthe phased antenna array 10 if the receiver means was disposed on theplane bisecting and perpendicular to line 20. The remote receiver meanswould then operate to null" or zero in the entire system by adjustingthe stand-by or zero input voltage generated by operational amplifier 92or, alternatively, by storing the output 94 from phase shifter 68 in anonillustrated integrating apparatus as an error voltage, for example.

The entire system can alternatively be switched from actual measurementmodes to calibrate modes and back again on a periodic basis with a pilottone being generated during each calibrate mode, for example, todistinguish between the various intervals. In this fashion, accuracy ofthe angle deviation measurement can always be maintained.

Referring now to FIG. 6, an alternative form of a receiver meansutilized to receive signals having frequency components such asindicated in FIG. 3, is illustrated, this receiver means being similarin most respects to the receiver means of FIG. 5. The front end of thereceiver means of FIG. 6 again is a standard superheterodyne receivingapparatus front end containing elements 50 through 64 as discussed withrespect to the receiver of FIG. 5, the transmitted modulatingfrequenciesf f f andf, being taken as the output of the AM detector 64.The mode of operation of the receiver means 56 is similar to that of thereceiver means of FIG. in that each of the modulating frequenciesf f andf are removed from the detector output 64 by filters 96, 98 and 100,respectively, and are sent to respective phase detectors 102, 104 and106. In this instance, it is presumed that the reference modulatingfrequency f, comprises I00 KHZ, for example, and this referencemodulating frequency is removed from the composite detector output 64 byfilter 108 and is coupled as one input to a phase detector 110. Theother input to phase detector 110 comprises the output of a voltagecontrolled crystal oscillator 112 constructed to have a normal orreference frequency of 100 KHZ and being controlled by the voltage oncontrol line 114.

The output from the voltage controlled crystal oscillator 112 providesthe second input to phase detector 110 and also provides an input to avernier means 116 as well as to a divider means 118 as will be describedhereinbelow. The output from the 100 KHZ filter 108 provides a second orcomparison input to the vernier means 116 whereas the output from thephase detector means 110 is coupled to an up-down counter 120, twooutputs from the phase detector means 110 being necessary so as toindicate counts in either the positive or the negative direction,depending on the direction of deviation of the phase of the voltagecontrolled oscillator 112 output with respect to the phase of the signalfrom the 100 KHZ filter 108 output.

Now, the receiver of FIG. 6 is initially activated during the calibrateor zeroeing" operation discussed above with respect to the receiver ofFIG. 5. At this time, each of the modulation signals f,,f ,f and f, areapplied to the reference antenna 12 of the phased an tenna array suchthat the receiver means receives a signal simulating the signal that thereceiver would receive had the receiver been disposed on a planeperpendicular to and bisecting line of the antenna array. During thiscalibrate interval, the receiver is placed in a calibrate mode, gate 122is opened during the present of the pilot tone allowing the errorsignals from the output of phase detectors 102, 104 and 106 to passthrough integrating amplifiers 124 and 126 to exercise control of thevoltage controlled oscillator 112 over its control line 114. The outputsfrom phase detectors 102, 104 and 106 are representative of thedifference in phase between the modulation signals f ,f and f, asactually received compared with the phase of signalsf f and f assynthesized by the interaction of the voltage controlled oscillator 112with the divider means 118.

During the actual calibrate period, gate 122 is opened such that as manycalibrated intervals as are necessary can be utilized to null or zerothe entire system. When the null or zero point is reached, the updowncounter 120 may be manually re-set to a predetermined count and thegating operation is then reversed such that the gate is opened duringthe measurement interval in the absence of the pilot tone and closedduring the calibrate interval or period. The frequency of voltagecontrol oscillator 112 is then corrected so as to provide an errorcount. The up-down counter 120 effectively counts the number of cycleseither gained or lost by the voltage controlled oscillator 112 withrespect to the 100 KHZ signal that is received and passes through thefilter 108. This count is obtained from the two outputs of phasedetector 1 10 and, as explained above, two outputs are necessary so asto control the up-down polarity of the counter 120. When null or zero isobtained, the up-down counter 120 would contain or store a countproportional to the size of the angle that the receiver position makesfrom the plane bisecting and perpendicular to line 20 of the array. Avernier reading may be obtained in the vernier 116 by measuring thephase displacement between the KHZ signal received at the output offilter means 108 and the 100 KHZ signal generated by the voltagecontrolled oscillator 112.

With respect to the above-described configuration of the transmittingarray 10 of FIG. 1, for example, which array transmits the frequencycomponents of FIG. 3, for example, which components are received by thereceiver of FIG. 5, a mathematical analysis can be performed indicatingthe internal operations and the manner in which the desired angularinformation can be extracted at the receiver.

Consider two antennas separated by a predetermined number, M,wavelengths of the carrier frequency. The direction perpendicular to theline joining the two antennas will be called the bore sight of thearray. Let one antenna be called the reference antenna S, and the otherbe called S Let m 21rf f carrier frequency w, 21rf,,,, f}, modulatingfrequency at S; I

d: difference phase from respective transmitting antenna to receiver inradians at o receiver near the bore sight.

Nm,,,= radian frequency of modulation at S A, amplitude of carrier Mmodulation amplitude The signal broadcast at S, contains threefrequencies,

fmfn+ m and fc fmi that E, =A Cosw t kA M CosUn co t A M CosUn cu I Thesignal transmitted from S has the carrier and lower sideband suppressed,hence,

E rA M CosUu t Nw t) The signal received from S will be shifted by anangle (b with respect to the phase of the reference signal. Denote thisby E and The received signal is the linear sum of these signals and thedetected signal is E (E,- E' Cos m t We consider here only the usefulcomponents of the detected signal and call it E,,.

The reference modulation component (Cosw t) is frequency multiplied by Nto produce CosNw t. This new component multiplied in a phase detectorwith the received component from S Cos(Nw,,,t 4)) to produce theinformation term.

Ignoring amplitude factors, the output of the phase detector is E; CosNwt [Cos (Nw t 100 ;[Cos(2Nw,,,t (b) Cos (1)] The dc component Cos d: isthe desired information. The one component which would have canceled theCos 4) term had it been transmitted, is the lower sideband from themodulator at S and it was eliminated to prevent such a cancellation.None of the terms omitted from this shortened analysis cancels theinformation term in the detected signal, as has been shown by a rigorousanalysis.

The above discussion and analysis has assumed that the antenna arraytransmits a plurality of signals having frequency components such asindicated in FIG. 3. However, and as discussed, the novel transmittingmeans of the instant invention can utilize double sideband suppressedcarrier modulations for each of the antennas 14, 16 and 18, of theantenna array, and in this manner, generate a composite signal havingthe frequency components of FIG. 4. With this inventive embodiment, amodification must be made in the receiver means of FIGS. 5 and 6 and, inthis respect, attention is now directed to the receiver means of FIG. 7particularly constructed in accordance with the instant invention tooperate with frequency components such as are present in FIG. 4.

Referring now to FIG. 7, the novel receiver will be seen to incorporatea standard so-called phase-lock front end comprising antenna 130, mixer132 coupled to a local oscillator 134, an amplifier stage 136, a secondmixer 138 coupled to a local oscillator 140, and an amplifier 142. Theoutput from amplifier 142 comprises one input to a phase detector 144,the other input to the phase detector being provided by a two megahertzoscillator 146 coupled through a divider 148 which produces an outputfrequency of 500 kilocycles. In this instance, we must assume a 500kilocycle intermediate frequency. Any difference between phase of thesignal generated by the oscillator I46 and subsequently divided in thedivider means 148 from the phase of the carrier signal received byantenna 130 provides an "error output fed through operational amplifier186 so as to control the frequency or phase of local oscillator 134. Inthis fashion, oscillator 146 is locked" to the received carrier signal.

As is shown, the output from the divider means 148, i. e., a 500kilocycle signal phase locked to the phase of the signal received byantenna 130, forms one input to phase detector 150, the other input tothe phase detector 150 being the composite signal as received by thereceiver means and as amplified by amplifier 142. The output of phasedetector 150 is then filtered in filter means 152 so as to recover a 5KHZ reference" signal which reference signal is utilized to reconstructthe other modulating frequencies, i.e.,f ,f andf Specifically, theoutput of filter 152 is fed either intact or as multiplied bymultipliers I54, 156 and 158, to a multi-position switch 160. Dependingon the position of switch 160, the input to a phase detector 162 willeither comprise a 5 KHZ signal, a 30 KHZ signal, a 35 KHZ signal, or a40 KHZ signal, these outputs being utilized to synthesize additionalsignals much in the fashion discussed with respect to receivers of FIGS.5 and 6.

Specifically, a phase detector 164 is provided with two inputs, oneinput being derived from the received, intermediate frequency signalfrom amplifier 142, the other input being derived from a voltagecontrolled oscillator 166, coupled through a divider 168 which serves todivide the frequency of oscillator 166 by four. The oscillator frequencyis itself controlled by the output of phase detector 162 throughoperational amplifier and high pass filter 170 as well as the output ofa logic circuit means 172.

The output from phase detector 164 comprises an amplitude proportionalto the cosine of the angular difference between the angle phase of areconstructed carrier corresponding to the suppressed carrier had itbeen transmitted of one of the modulation frequencies f ,f and f and thephase angle of the carrier actually transmitted. This amplitude is takenas the output of the receiver device on line 174. When the angulardifference between the angler of the synthesized or reconstructedcarrier and the angle of the carrier transmitted is the output on line174 is 0. As this phase varies to either side of 90, the signal wouldincrease and a l80 phase shift would occur about the null point. Theerror signal utilized to control this loop is contained in the amplitudeand with the 180 phase reversal. As is shown, the phase detector 162functions as a synchronous detector and is utilized to convert the errorsignal from phase detector 164 into bipolar DC, which DC signal drivesthe voltage controlled oscillator 166 through the amplifier 170. Theutilization of a single discrete frequency as selected by the positionof the multi-position switch as well as the utilization of a low cut-offfrequency in the feed-back amplifier 170 serves to separate the desiredmodulation tone from the composite received signal.

In effect, then, rather than directly comparing the modulatingfrequencies f jg, andfi as received with signals that are synthesized tohave the same frequencies, the receiver means of FIG. 7 utilizes thereference modulation tonef as a demodulating signal in thesynthesization or reconstruction of each of the respective suppressedcarriers of the modulating frequencies f f and f,. This operation ispossible since, as pointed out at the outset of this description, doublesideband suppressed carriers comprise the type of signal generated bythe antenna array 10 in this alternative though preferred inventiveembodiment.

The overall operation of the receiver means of FIG. 7 is such that aparticular reference tone is selected by the multi-selector switch 160and a carrier insertion into phase detector 164 is allowed to stabilize.The base or nominal frequency of voltage controlled oscillator 166 isprovided by logic circuit means 172 operable through a plurality ofdividers 174, 176 and 178, which dividers are coupled to an up-downcounter 180 as selectively provided by multi-position switch 182, gangedto the switch 160. The cycle shift between the zero standard and thevoltage controlled oscillator 166 is counted in the units counter which,in this instance, comprises divider 178. Now, the second reference toneis selected by multi-position switch 160 and the carrier insertion loopis again allowed to stabilize, any cycle shift between the new zerostandard and the voltage controlled oscillator 166 being counted in thefour's counter, i.e., divider means 176. Lastly, the remaining referencesignal is selected by multi-position switch 160 and the loop againallowed to stabilize, any cycle shift occurring being counted in the l6scounter. The entire process repeats itself and the reference" angle isconstantly updated.

As was similarly done with respect to a receiver means designed tooperate with transmitted frequencies of FIG. 3, a mathematical analysiscan be made of the operation of the receiver means of FIG. 7, thisreceiver means being designed to operate with frequency components ofFIG. 4. In this double sideband, suppressed carrier instance, thefollowing relationships hold true:

Carrier wt Modulation pt Sidebands sin p)t sin (1 p)t Injected Carriersin (mt 1b) Output of product and phase detector 164 cos (pt cos (2101+pt cos (-pt 11)) cos (2w! pt After L.P. filtering e cos (p! cos (-pt 4))e cos pt Cos d) sin I sind cos pt Cos sin I sinqi During the foregoingdiscussion of each of the above embodiments of the invention, thereceiver means itself was contemplated to not only receive the signalstransmitted by the transmitting antenna array 10, but to process suchreceived signals and particularly to compare the various phasestherebetween so as to generate an output indicative of the locus of thepositions of the receiver with respect to location of the transmittingantenna array. Still within the novel principles herein expressed, thereceiver means and the signal processing portion thereof may beseparated, desired, such that the signal processing portion or means isitself disposed at a location remote with respect to the transmittingantenna array and with respect to the receiver means. Means are providedso that calculations as to the location of the receiver means withrespect to the transmitting antenna array 10 can be made at a locationother than the receiver means itself.

Attention is herein initially invited to FIG. 8 of the instant drawingswherein one embodiment of the invention is disclosed with the receivermeans and the signal processing portion thereof being separated in themanner discussed. An antenna array 10 and an associated transmitter isprovided as is usual similar to the previous embodiments of the instantinvention disclosed in FIG. I, for example. The antenna array 10 iscontemplated to transmit a carrier having a plurality of referencemodulations thereon, this composite signal transmission beingrepresented by reference numeral 161 and being received by a remotereceiver-transmitter means 163. In the receiver-transmitter means 163,the composite signal 161 is demodulated and the modulation signalcomponents, each with its respective phase shift are recovered. Ratherthan comparing the relative phases in the receiver means 163 whereby therelative position of the receiver means can be fixed with respect to thetransmitting array 10, it is sufficient to accomplish this positionallocation objective if the component signals which are to be phasecompared are retransmitted to some other remote point without change inthe relative phase therebetween.

Accordingly, in this embodiment of the instant invention, the componentsignals received in the receivertransmitter 163 are retransmitted to afurther remote signal processing location generally designated 165 alongthe schematically illustrated path 167. Since only a single antenna isutilized by the receiver-transmitter means 163, any further change inthe relative phases of the component signals will be avoided.

The remote signal processing means will be seen to comprise a receivermeans 168 which serves to receive the component signals retransmitted bythe receiver-transmitter means 163 and compare the phases therebetweenin a comparator means 169 to thereby provide the system output. Suchsystem output, as in past embodiments, will be representative of theposition of the remote receiver-transmitter means 163 with respect tothe transmitting antenna array 10.

FIG. 9 depicts a block diagram schematic of a suitablereceiver-transmitter means such as is designated by reference numeral163 in the system of FIG. 8. The receiver-transmitter means will be seento comprise, in a preferred embodiment thereof, a diplexer 171 ofconventional construction for the purpose of allowing a single antenna173 to be utilized both for receiving and for transmitting. The receiverportion of the receivertransmitter means 163 includes a mixer 175, alocal oscillator 177, an IF amplifier 179, and an AM detector means 181which serves to detect the frequency components of the composite signaltransmitted by the antenna array 10 whereby the reference modulationcomponent and the information modulation component are recovered. Thesesignals are utilized in a modulator means 183 to modulate a carrierhaving a frequency different from that of the received carrier. Themodulator output then passes through a transmitter means 185 and thediplexer means 171 back to the antenna 173.

A still further variation of this particular form of the novel inventionis that wherein the receiver-transmitter means 163 comprises aconventional transponder apparatus which serves to change the frequencyof the received composite signal, amplify this signal and pass thesignal through a diplexer to the antenna. With this alternative form aswell as the modification abovediscussed, the receiver-transmitter means163 must be designed to preserve the relative phases of the componentsof the composite signals received so as not to destroy informationrepresentative of the angular position of the receiver-transmittermeans.

With an embodiment of the invention of the type wherein thesignal-processer means is separate and remote from thereceiver-transmitter means, the separate processing location may betime-shared to process data and display positions for a large number ofremote mobile units comprising receiver-transmitter means. This, plusthe fact that the processing equipment utilized here need not beminiaturized for mobility suggests that a larger and faster digitalcomputer might be provided. Also, means are provided to store and/ordisplay many mobile unit positions, which additional equipment would notbe needed in the case where each mobile unit processes the signals whichcontain its own position information. In the case of time sharing,control of the time sharing process may be placed in the computerprogram. The computer may address a mobile unit causing it to turn onits transmitter and switch the receiver channel to receive signals fromone array and the processor would derive on the ground the locus of themobile units position. The mobile unit input would be switched to thefrequency of another array and the process repeated. The intersection ofthe two locii is the mobile units position. If a third array isavailable,

.the process is repeated for a check on the results or to improve theaccuracy of the computed position. When the mobile unit comprises atransponder, there is a choice of processing the signals at thetransponded frequency or changing back to the original frequency beforeprocessing the signals.

A modification of the inventive embodiment depicted in FIG. 8 is shownin FIG. 11 and attention is therein invited. As will be seen, theinventive embodiment of FIG. 11 is similar to that of FIG. 8 in that thesignal processing portion of the receiver means is separate and isitself disposed at a location remote with respect to the transmittingantenna array and with respect to the receiver means. However, thetechnique by which the angular position of the remote receiver means isdetermined is somewhat different, as is the manipulation of thecomposite signal transmitted by the transmitting antenna array 10.

Referring initially to FIG. 10, the frequencies contemplated fortransmission by the antenna array 10 in this further embodiment of theinstant invention are schematically represented. Here, only threespacedapart antennas 190, 192, and 194 are contemplated for use asdepicted in FIG. 11. Antenna 190 is contemplated to generate a referencesignal which, in this instance, comprises a carrier f... The additionalantennas 192 and 194 are each contemplated to generate suppressedcarrier, single sideband signals modulated by frequencies f +f and f +frespectively.

A receiver/transmitter means 196 is provided at some unknown locationremote from the location of the antenna array 10 and this means 196serves to receive and detect the composite signal such as in FIG. 10generated from the antenna array. Whereas in previous embodiments, thereceiver means 196 would detect the modulating signals and comparephases of the detected signals to determine the angular deviation 6! ofthe receiver means 196 from a plane 198, for example, bisecting andperpendicular to the line 200 between two of the transmitting antennas190, I92 and 194, the receiver/transmitter means 196 in this instance,as was the case with respect to FIG. 8, serves only to retransmit alongpath 202, for example, the detected signals received from the antennaarray 10 along path 204.

Again, no additional relative phase displacements occur between variousfrequency components of the detected signals retransmitted by 196 sinceonly a single transmitting antenna is utilized. The receiver 207 of thesignal processing means 206 serves to receive the combined compositesignal from the transceiver means 196 along line 202, and receiver 208serves to receive the composite signal transmitted by the antenna array10 along line or directions 212. The processing means 206 then comparesthe various phases of the components of the signals received astransmitted by means 196, and as transmitted by the antenna of array 10,such phase comparison taking place in a comparator means 210. Thelocation of the signal processing means 206, though remote from theantenna array 10 as well as from the means 196 is a known location atleast with respect to the angular deviation [3 of the remote signalprocessing means from the plane 198 bisecting and perpendicular to theline 200 between two of the transmitting antennas. Accordingly, sincethe relative angular position of the signal processing means 206 withrespect to the antenna array 10 is known, the comparison made betweenthe phases of the various frequency components of the signalstransmitted by the antenna array and re-transmitted by means 196 andreceived by the signal processor means 206 is effective to againdetermine the angular position of the remote receiver/- transmittermeans 196.

The particular hardware utilized in the embodiment of FIG. 9 can beselected, with obvious modification, from that disclosed in thepreceding figures as it should be understood that the underlyingprinciples and concepts of this embodiment of the novel invention remainthe same as depicted hereinbefore. The primary difference resides in thefact that the signal processing function is physically separated fromthe remote receiver means. Likewise, many variations can be made to thefrequency makeup of the composite signal transmitted by the antennaarray 10 as was the case in past examples.

The novel invention further provides for yet another modificationthereof and attention is herein direct to FIGS. 12 and 13 of thedrawings. Again, it will be assumed that, in this embodiment, only threetransmitting antennas comprise the antenna array 10. The first orreference transmitter is contemplated to transmit a signal having acarrier f modulated with two single sidebandsf andfl the differencefrequency between these two modulating sidebands (f -f,) being known.The remaining antennas of the antenna array are contemplated to transmita suppressed carrier single sideband signal, one of such antennastransmitting a frequency f,.+f the other of the antennas transmitting afrequency f +f frequenciesf andf, being multiples of the differencefrequency f f,.

Now a remote receiver means is provided such as depicted in FIG. 13, foruse with the instant invention as generally described with respect toFIGS. 1 through 7 of the instant drawings. The receiver means of FIG.13, however, is specifically constructed so as to operate withtransmitted frequencies such as shown in FIG. 12.

Referring, now, to FIG. 13, the receiver means therein illustrated willbe seen to include a detector means 212 functioning in the normalfashion to demodulate signals received by antenna 214 so as to removethe various sideband modulating frequencies f f f andf in accordancewith the transmitted wave form of FIG. 12.

The composite demodulated signal from the detector means 212 is then fedto a plurality of filter means 214, 216, 218 and 220, wherein theindividual frequencies f,,f ,f', and f respectively, are recovered. Theoutput from filters 214 and 216 is fed into a frequency differencedetector 222 wherein the difference frequency f -f, is generated withthe same phase as received frequencies f, and f and is subsequentlypassed to frequency multipliers 224 and 226 wherein this differencefrequency is multipled to equal the frequency off and 1",, respectively.

Frequency components f and f, as received by the receiver means of FIG.11, pass through filter means 218 and 220, respectively, into respectivephase detec tors 228 and 230. In phase detector 228, for example, theregenerated or synthesized frequency component f from frequencymultiplier 224 is phase compared with frequency componentf as actuallyreceived by the receiver means from filter means 218 and an error outputis generated. Likewise, the phase difference between the phase orfrequency component f, as actually received and frequency component f,as regenerated or synthesized is compared in phase detector 230 and anerror output is generated. This error output is indicative of theangular deviation of the receiver means from the transmitting antennaarray in the same fashion as was the case in the previously discussedexamples of the invention.

As should now be apparent, the objects initially set forth at the outsetto this specification have been successfully achieved. Accordingly,

What is claimed is l. A radio communication system comprising atransmitting antenna array defining a plurality of spacedapart antennas,transmission means coupled to said antenna array such that one antennatransmits a reference frequency signal, and such that each other antennatransmits a signal having respectively different frequencycharacteristics than said reference frequency signal; remotereceiver-transmitter means for receiving the composite transmittedsignals and for retransmitting at least some of said signals withoutrelative phase shift therebetween, a signal processor means disposed ata remote location with respect to said antenna array for receiving saidretransmitted signals from said receiver-transmitter means and saidcomposite signals transmitted from said antenna array, said signalprocessor means including comparator means for comparing the phase ofsaid received signals from the receivertransmitter means with the phaseof received signals of like frequency characteristics from thetransmitting antenna array and for generating an output therefromindicative of the locus of the positions of said receivertransmittermeans with respect to the location of said transmitting antenna array.

2. A radio communication system as defined in claim 1 wherein saidremote receiver-transmitter means retransmits said signals from a singleantenna and at a different carrier frequency than the carrier frequencyof said signals transmitted from said antenna array.

3. A radio communication system comprising a plurality of transmittingantenna means, one of said antenna means transmitting a reference signalcomprising a carrier and a plurality of single sidebands having a givenfrequency difference therebetween, each of the other antenna meanstransmitting a suppressed carrier signal having a respectively differentsingle sideband modulating frequency component, receiver system meansfor said transmitted signals disposed at a remote location, saidreceiver means having radio antenna means and including means fordetecting said reference signal and said frequency difference betweenthe sidebands thereof and for synthesizing each of said respectivelydifferent modulating frequency components therefrom, said receiversystem means further including comparator means for selectivelycomparing the phase of said synthesized signals with the phase of thetransmitted signals, said receiver system means generating an outputfrom the compared phase differentials representative of the locus of thereceiver antenna positions with respect to said plurality of antennameans.

4. A system as defined in claim 3, wherein said comparator means of saidreceiver multiplies said first signal by a given multiple to produce athird signal having the same frequency as the frequency of said secondsignal, and compares the phase of said third signal with the phase ofsaid second signal to generate said output.

5. A system as defined in claim 4, including additional spaced-aparttransmitting antennas, each transmitting a wave comprising respectivelydifferent modulating signals, each said different modulating signalcomprising a frequency having a different multiple of said firstmodulating frequency, said comparator means of said receiver selectivelymultiplying said first signal by each said different multiple torespectively produce a plurality of third signals each having the samefrequency as the frequency of a respective different modulating signal,each said third signal being phasecompared with the phase of saidrespective different modulating signal to generate said output.

6. A system as defined in claim 5, wherein said reference wave comprisesan amplitude modulated carrier and wherein said other transmitted wavescomprise suppressed carrier single sideband amplitude modulated signals.

7. A system as defined in claim 5, wherein said second and each saidadditional transmitting antenna is disposed at different distances fromsaid first transmitting antenna, said distances bearing the samerespective relationship with one another as the relationship between thedifferent multiples of the transmitted modulating frequencies.

8. A system as defined in claim 4, wherein said reference wave comprisesan amplitude modulated carrier and wherein said wave transmitted by saidsecond antenna comprises an amplitude modulated suppressed carrierhaving a double sideband, said comparator means of said receiverinternally regenerating said suppressed carrier from the received doublesidebands, said regenerated carrier comprising said third signal, andwherein said comparator means compares the phase of said regeneratedcarrier with the phase of said transmitted carrier of said referencewave to produce said output.

9. A radio communication system as defined in claim 5, wherein saidreference wave comprises an amplitude modulated carrier and wherein saidother transmitted waves comprise amplitude modulated suppressed carriershaving double sidebands, said comparator means of said receiverinternally regenerating the suppressed carriers from the received doublesidebands, said regenerated carriers comprising said third signals, andwherein said comparator means compares the phase of each saidregenerated carrier with the phase of said transmitted carrier of saidfirst signal to produce said output.

10. A radio communication system as defined in claim 5, wherein theoutput of said receivermeans indicates the angular deviation of thelocation of said receiver antenna from a plane bisecting andperpendicular to a line between two of said transmittirig antennas.

11. A radio communication system as defined in claim 5, furtherincluding calibration mean associated with said transmission means, suchthat sai first transmitting antenna selectively and simultaneouslytransmits all of said signals, the other transmitting antennas beinginoperative.

12. A radio communication system as defined in claim 3, wherein each ofsaid other antenna means transmits a suppressed carrier double sidebandsignal.

13. A radio communication system as, defined in claim 3, wherein each ofsaid other ante'nna means transmits a suppressed carrier single sidebandsignal.

14. A radio communication system comprising:

a transmitter means including first antenna means for generating andtransmitting a first signal having a first frequency component, andadditional spaced antenna means for generating and transmitting othersignals having respectively different frequency components each being amultiple of said first frequency component; and

a receiver system including means for receiving said transmittedsignals, means for synthesizing from said first signal additionalsignals having frequency components that are the same as said othertransmitted signals, and means for comparing the phases of saidsynthesized signals respectively with the phases of said othertransmitted signals having the same frequency to provide an outputrepresentative of the position of the receiving means relative to thetransmitter means.

15. A radio communication system as defined in claim 14, wherein saidfirst signal comprises an amplitude modulated carrier and wherein saidother signals comprise single sideband amplitude modulated suppressedcarriers.

16. A radio communication system as defined in claim 14, wherein saidfirst signal comprises an amplitude modulated carrier and wherein saidother signals comprise double sideband amplitude modulated suppressedcarriers and wherein said means for synthesizing serves to synthesizecarrier signals having the same phase angle as would said suppressedcarriers, had said suppressed carriers been transmitted.

17. A radio communication system comprising: an antenna array includingat least two antennas, means for generating a first signal comprising acarrier modulated by a first signal frequency to be transmitted over afirst antenna, means for generating other signals by modulating thecarrier by signals of other frequencies, each of said signals to betransmitted over a different antenna and a receiver system includingmeans for receiving said transmitted signals, said receiver systemfurther including means for deriving from the received composite signaleach of the modulating signals, means for synthesizing from the firstmodulating signal, signals having respectively the frequencies of eachof other said modulating signals, phase comparison means for comparingthe phase of the derived modulating signal of like frequency, and meansfor deriving from said phase comparisons the angular position of saidreceiving means with respect to lines joining the pairs of transmittingantennas.

18. A radio communication system as defined in claim 17, wherein thefirst signal comprises an amplitude modulated carrier and wherein saidother signals comprise single sideband amplitude modulated carriersignals with carriers suppressed.

19. A radio communication system as defined in claim 17, wherein thefirst signal comprises an amplitude modulated carrier and wherein saidother signals comprise double sideband amplitude modulated carriersignals with carriers suppressed, and wherein said means forsynthesizing serves to synthesize carrier signals having respectivelythe same phase angles at the receiver as would said suppressed carriershad said suppressed carriers been transmitted.

20. A radio communication system as defined in claim 17, wherein firstsaid signal comprises a carrier, and single sidebands from each of twomodulating frequencies, and wherein each other transmitted signal is asingle sideband amplitude modulated signal with carrier suppressed andwherein each of the other modulating frequencies is a multiple of thedifference of the two frequencies modulating the carrier to producefirst said signal.

21. A radio communication system as defined in claim 17, wherein saidsignal synthesizing, phase comparing and angular position determiningmeans of the receiver system are separated from the receiving means, andconnected to said receiving means by a radio link, whereby the derivedmodulation signals are transmitted from the receiving means to thelocation of the other said means without relative phase shift among saidderived modulation signals.

22. A radio communication system as defined in claim 18, wherein saidsignal synthesizing, phase comparing and angular position determiningmeans of the receiver system are separated from the receiving means, andconnected to said receiving means by a radio link, whereby the derivedmodulation signals are transmitted from the receiving means to thelocation of other said means without relative phase shift among saidderived modulation signals.

23. A radio communication system as defined in claim 19, wherein saidsignal synthesizing, phase comparing and angular position determiningmeans of the receiver system are separated from the receiving means, andconnected to said receiving means by a radio link, whereby the derivedmodulation signals are transmitted from the receiving means to thelocation of other said means without relative phase shift among saidderived modulation signals.

24. A radio communication system as defined in claim 14, wherein saidsignals synthesizing and phase comparison means of the receiver systemare physically separated from the receiving means and are operationallyconnected thereto by means of a radio link.

#l it i

1. A radio communication system comprising a transmitting antenna arraydefining a plurality of spaced-apart antennas, transmission meanscoupled to said antenna array such that one antenna transmits areference frequency signal, and such that each other antenna transmits asignal having respectively different frequency characteristics than saidreference frequency signal; remote receiver-transmitter means forreceiving the composite transmitted signals and for retransmitting atleast some of said signals without relative phase shift therebetween, asignal processor means disposed at a remote location with respect tosaid antenna array for receiving said retransmitted signals from saidreceiver-transmitter means and said composite signals transmitted fromsaid antenna array, said signal processor means including comparatormeans for comparing the phase of said received signals from thereceiver-transmitter means with the phase of received signals of likefrequency characteristics from the transmitting antenna array and forgenerating an output therefrom indicative of the locus of the positionsof said receiver-transmitter means with respect to the location of saidtransmitting antenna array.
 2. A radio communication system as definedin claim 1 wherein said remote receiver-transmitter means retransmitssaid signals from a single antenna and at a different carrier frequencythan the carrier frequency of said signals transmitted from said antennaarray.
 3. A radio communication system comprising a plurality oftransmitting antenna means, one of said antenna means transmitting areference signal comprising a carrier and a plurality of singlesidebands having a given frequency difference therebetween, each of theother antenna means transmitting a suppressed carrier signal having arespectively different single sideband modulating frequency component,receiver system means for said transmitted signals disposed at a remotelocation, said receiver means having radio antenna means and includingmeans for detecting said reference signal and said frequency differencebetween the sidebands thereof and for synthesizing each of saidrespectively different modulating frequency components therefrom, saidreceiver system means further including comparator means for selectivelycomparing the phase of said synthesized signals with the phase of thetransmitted sIgnals, said receiver system means generating an outputfrom the compared phase differentials representative of the locus of thereceiver antenna positions with respect to said plurality of antennameans.
 4. A system as defined in claim 3, wherein said comparator meansof said receiver multiplies said first signal by a given multiple toproduce a third signal having the same frequency as the frequency ofsaid second signal, and compares the phase of said third signal with thephase of said second signal to generate said output.
 5. A system asdefined in claim 4, including additional spaced-apart transmittingantennas, each transmitting a wave comprising respectively differentmodulating signals, each said different modulating signal comprising afrequency having a different multiple of said first modulatingfrequency, said comparator means of said receiver selectivelymultiplying said first signal by each said different multiple torespectively produce a plurality of third signals each having the samefrequency as the frequency of a respective different modulating signal,each said third signal being phase-compared with the phase of saidrespective different modulating signal to generate said output.
 6. Asystem as defined in claim 5, wherein said reference wave comprises anamplitude modulated carrier and wherein said other transmitted wavescomprise suppressed carrier single sideband amplitude modulated signals.7. A system as defined in claim 5, wherein said second and each saidadditional transmitting antenna is disposed at different distances fromsaid first transmitting antenna, said distances bearing the samerespective relationship with one another as the relationship between thedifferent multiples of the transmitted modulating frequencies.
 8. Asystem as defined in claim 4, wherein said reference wave comprises anamplitude modulated carrier and wherein said wave transmitted by saidsecond antenna comprises an amplitude modulated suppressed carrierhaving a double sideband, said comparator means of said receiverinternally regenerating said suppressed carrier from the received doublesidebands, said regenerated carrier comprising said third signal, andwherein said comparator means compares the phase of said regeneratedcarrier with the phase of said transmitted carrier of said referencewave to produce said output.
 9. A radio communication system as definedin claim 5, wherein said reference wave comprises an amplitude modulatedcarrier and wherein said other transmitted waves comprise amplitudemodulated suppressed carriers having double sidebands, said comparatormeans of said receiver internally regenerating the suppressed carriersfrom the received double sidebands, said regenerated carriers comprisingsaid third signals, and wherein said comparator means compares the phaseof each said regenerated carrier with the phase of said transmittedcarrier of said first signal to produce said output.
 10. A radiocommunication system as defined in claim 5, wherein the output of saidreceiver means indicates the angular deviation of the location of saidreceiver antenna from a plane bisecting and perpendicular to a linebetween two of said transmitting antennas.
 11. A radio communicationsystem as defined in claim 5, further including calibration meansassociated with said transmission means, such that said firsttransmitting antenna selectively and simultaneously transmits all ofsaid signals, the other transmitting antennas being inoperative.
 12. Aradio communication system as defined in claim 3, wherein each of saidother antenna means transmits a suppressed carrier double sidebandsignal.
 13. A radio communication system as defined in claim 3, whereineach of said other antenna means transmits a suppressed carrier singlesideband signal.
 14. A radio communication system comprising: atransmitter means including first antenna means for generating andtransmitting a first signal having a first frequency component, andadditional Spaced antenna means for generating and transmitting othersignals having respectively different frequency components each being amultiple of said first frequency component; and a receiver systemincluding means for receiving said transmitted signals, means forsynthesizing from said first signal additional signals having frequencycomponents that are the same as said other transmitted signals, andmeans for comparing the phases of said synthesized signals respectivelywith the phases of said other transmitted signals having the samefrequency to provide an output representative of the position of thereceiving means relative to the transmitter means.
 15. A radiocommunication system as defined in claim 14, wherein said first signalcomprises an amplitude modulated carrier and wherein said other signalscomprise single sideband amplitude modulated suppressed carriers.
 16. Aradio communication system as defined in claim 14, wherein said firstsignal comprises an amplitude modulated carrier and wherein said othersignals comprise double sideband amplitude modulated suppressed carriersand wherein said means for synthesizing serves to synthesize carriersignals having the same phase angle as would said suppressed carriers,had said suppressed carriers been transmitted.
 17. A radio communicationsystem comprising: an antenna array including at least two antennas,means for generating a first signal comprising a carrier modulated by afirst signal frequency to be transmitted over a first antenna, means forgenerating other signals by modulating the carrier by signals of otherfrequencies, each of said signals to be transmitted over a differentantenna and a receiver system including means for receiving saidtransmitted signals, said receiver system further including means forderiving from the received composite signal each of the modulatingsignals, means for synthesizing from the first modulating signal,signals having respectively the frequencies of each of other saidmodulating signals, phase comparison means for comparing the phase ofthe derived modulating signal of like frequency, and means for derivingfrom said phase comparisons the angular position of said receiving meanswith respect to lines joining the pairs of transmitting antennas.
 18. Aradio communication system as defined in claim 17, wherein the firstsignal comprises an amplitude modulated carrier and wherein said othersignals comprise single sideband amplitude modulated carrier signalswith carriers suppressed.
 19. A radio communication system as defined inclaim 17, wherein the first signal comprises an amplitude modulatedcarrier and wherein said other signals comprise double sidebandamplitude modulated carrier signals with carriers suppressed, andwherein said means for synthesizing serves to synthesize carrier signalshaving respectively the same phase angles at the receiver as would saidsuppressed carriers had said suppressed carriers been transmitted.
 20. Aradio communication system as defined in claim 17, wherein first saidsignal comprises a carrier, and single sidebands from each of twomodulating frequencies, and wherein each other transmitted signal is asingle sideband amplitude modulated signal with carrier suppressed andwherein each of the other modulating frequencies is a multiple of thedifference of the two frequencies modulating the carrier to producefirst said signal.
 21. A radio communication system as defined in claim17, wherein said signal synthesizing, phase comparing and angularposition determining means of the receiver system are separated from thereceiving means, and connected to said receiving means by a radio link,whereby the derived modulation signals are transmitted from thereceiving means to the location of the other said means without relativephase shift among said derived modulation signals.
 22. A radiocommunication system as defined in claim 18, wherein said signalsynthesizing, phase comparing and angular position determining means ofthe receiver system are separated from the receiving means, andconnected to said receiving means by a radio link, whereby the derivedmodulation signals are transmitted from the receiving means to thelocation of other said means without relative phase shift among saidderived modulation signals.
 23. A radio communication system as definedin claim 19, wherein said signal synthesizing, phase comparing andangular position determining means of the receiver system are separatedfrom the receiving means, and connected to said receiving means by aradio link, whereby the derived modulation signals are transmitted fromthe receiving means to the location of other said means without relativephase shift among said derived modulation signals.
 24. A radiocommunication system as defined in claim 14, wherein said signalssynthesizing and phase comparison means of the receiver system arephysically separated from the receiving means and are operationallyconnected thereto by means of a radio link.